I haven't hit the rocks seriously yet with my portals, waiting till I get another set of tires but I'm running 6" 45% with 37s and SATV isnt joking when they say it's a total game changer. I've done a few things that I know at the very least would have blown an axle, possibly a diff but it hasn't batted an eye. Beefed everything up to support it but like Supersmith says those 4s are going to be alot less strain on everything than the 6s. Definitely keep everything torqued, you have to be meticulous in your pre ride checks. I had my toe rod bolts back off and lost a DS toe rod on the trail. Pretty much the only thing I'm left wanting for at this point is valving.
If you're thinking of getting them and you think you fit the market which it sounds like you do, I couldn't recommend them more highly.